Motional Electromotive Force: Overview, Questions, Preparation

Updated on Sep 17, 2025 17:18 IST

Motional EMF is referred to the difference occurring in the conductor when moved through a magnetic field. When we move the conductor through a magnetic field, the free charges experience a magnetic push, which leads to the production of voltage. This law is a direct result of faraday’s law of electromagnetic induction and is one of the most crucial topics of the chapter electromagnetism. Candidates who are considering preparing for JEE MAINS should definitely go through every core detail of this concept.

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Table of content

Basic Concept
Mathematical Formula
Real-World Applications
Physics Class 12 NCERT Solutions

Basic Concept

Suppose a conductor is moved through a magnetic field. The free charges (electrons) in the conductor will start to experience a magnetic force known as Lorentz force. This force will push them towards one end of the conductor. Due to this movement, a potential difference called motional EMF is created which leads to the production of voltage.

This magnetic field helps in the production of electricity that can be used in various day to day scenarios.

Mathematical Formula

This motional EMF can be represented by the general equation:

E=(v×B)⋅l

Where,

E: Motional EMF

V: Velocity

B: Magnetic Field

L: Length of the conductor

Note: In cases where l is perpendicular to both v and b, the formula is denoted as:

E=Blv

Real-World Applications

This isn’t just limited to theory. The concept of Motional EMF has a wide range of uses in our day to day used appliances, some of which are as follows:

Generators and motors
Railguns
Magnetic Meters
Aeroplanes
Wind Turbines
Powerplants

Physics Class 12 NCERT Solutions

Sl. No	Name of Chapter
1	Electric Charges and Fields
2	Electrostatic Potential and Capacitance
3	Current Electricity
4	Moving Charges and Magnetism
5	Magnetism and Matter
6	Electromagnetic Induction
7	Alternating Current
8	Electromagnetic Waves
9	Ray Optics and Optical Instruments
10	Wave Optics
11	Dual Nature of Radiation and Matter
12	Atoms
13	Nuclei
14	Semiconductor Electronics: Materials, Devices and Simple Circuits

Commonly asked questions

What is the major cause of Motional EMF? Electric field or Magnetic field?

The movement of the body in the conductor is caused by the magnetic field. This magnetic field then causes an electric current to flow in the system. Hence, the direct action is caused by the magnetic force on the object, due to which it becomes the major source of motional EMF.

What is the difference between motional emf and induced emf?

Motional EMF is a condition which arises due to the movement of conductor in a magnetic field. On the other hand, induced EMF is a cause of change in the magnetic fiedl over a certain timespan. Induced EMF arises when there is a change in the magnetic flux.

Which factors don't affect motional EMF?

Here are a few factors which are not responsible for affecting the motional EMF: